/**
 * Created by SLICE_30_K on 2017/5/22.
 *
 * 支持一般Base64的编码和解码
 * 支持符合RFC_4648标准中"URL and Filename Safe Alphabet"的URL安全Base64编解码
 * 支持中文字符的编解码(Unicode编码)
 */
;(function (root, factory) {
	if (typeof exports === "object") {
		// CommonJS
		module.exports = exports = factory();
	}
	else if (typeof define === "function" && define.amd) {
		// AMD
		define(factory);
	}
	else {
		// Global (browser)
		window.BASE64 = factory();
	}
}(this, function () {
	var BASE64_MAPPING = [
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
		'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
		'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
		'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
		'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
		'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
		'w', 'x', 'y', 'z', '0', '1', '2', '3',
		'4', '5', '6', '7', '8', '9', '+', '/'
	];
	var URLSAFE_BASE64_MAPPING = [
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
		'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
		'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
		'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
		'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
		'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
		'w', 'x', 'y', 'z', '0', '1', '2', '3',
		'4', '5', '6', '7', '8', '9', '-', '_'
	];

	var _toBinary = function (ascii) {
		var binary = [];
		while (ascii > 0) {
			var b = ascii % 2;
			ascii = Math.floor(ascii / 2);
			binary.push(b);
		}
		binary.reverse();
		return binary;
	};

	var _toDecimal = function (binary) {
		var dec = 0;
		var p = 0;
		for (var i = binary.length - 1; i >= 0; --i) {
			var b = binary[i];
			if (b == 1) {
				dec += Math.pow(2, p);
			}
			++p;
		}
		return dec;
	};

	var _toUTF8Binary = function (c, binaryArray) {
		var mustLen = (8 - (c + 1)) + ((c - 1) * 6);
		var fatLen = binaryArray.length;
		var diff = mustLen - fatLen;
		while (--diff >= 0) {
			binaryArray.unshift(0);
		}
		var binary = [];
		var _c = c;
		while (--_c >= 0) {
			binary.push(1);
		}
		binary.push(0);
		var i = 0, len = 8 - (c + 1);
		for (; i < len; ++i) {
			binary.push(binaryArray[i]);
		}

		for (var j = 0; j < c - 1; ++j) {
			binary.push(1);
			binary.push(0);
			var sum = 6;
			while (--sum >= 0) {
				binary.push(binaryArray[i++]);
			}
		}
		return binary;
	};

	var _toBinaryArray = function (str) {
		var binaryArray = [];
		for (var i = 0, len = str.length; i < len; ++i) {
			var unicode = str.charCodeAt(i);
			var _tmpBinary = _toBinary(unicode);
			if (unicode < 0x80) {
				var _tmpdiff = 8 - _tmpBinary.length;
				while (--_tmpdiff >= 0) {
					_tmpBinary.unshift(0);
				}
				binaryArray = binaryArray.concat(_tmpBinary);
			} else if (unicode >= 0x80 && unicode <= 0x7FF) {
				binaryArray = binaryArray.concat(_toUTF8Binary(2, _tmpBinary));
			} else if (unicode >= 0x800 && unicode <= 0xFFFF) {//UTF-8 3byte
				binaryArray = binaryArray.concat(_toUTF8Binary(3, _tmpBinary));
			} else if (unicode >= 0x10000 && unicode <= 0x1FFFFF) {//UTF-8 4byte
				binaryArray = binaryArray.concat(_toUTF8Binary(4, _tmpBinary));
			} else if (unicode >= 0x200000 && unicode <= 0x3FFFFFF) {//UTF-8 5byte
				binaryArray = binaryArray.concat(_toUTF8Binary(5, _tmpBinary));
			} else if (unicode >= 4000000 && unicode <= 0x7FFFFFFF) {//UTF-8 6byte
				binaryArray = binaryArray.concat(_toUTF8Binary(6, _tmpBinary));
			}
		}
		return binaryArray;
	};

	var _toUnicodeStr = function (binaryArray) {
		var unicode;
		var unicodeBinary = [];
		var str = "";
		for (var i = 0, len = binaryArray.length; i < len;) {
			if (binaryArray[i] == 0) {
				unicode = _toDecimal(binaryArray.slice(i, i + 8));
				str += String.fromCharCode(unicode);
				i += 8;
			} else {
				var sum = 0;
				while (i < len) {
					if (binaryArray[i] == 1) {
						++sum;
					} else {
						break;
					}
					++i;
				}
				unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 1, i + 8 - sum));
				i += 8 - sum;
				while (sum > 1) {
					unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 2, i + 8));
					i += 8;
					--sum;
				}
				unicode = _toDecimal(unicodeBinary);
				str += String.fromCharCode(unicode);
				unicodeBinary = [];
			}
		}
		return str;
	};

	var _encode = function (str, url_safe) {
		var base64_Index = [];
		var binaryArray = _toBinaryArray(str);
		var dictionary = url_safe ? URLSAFE_BASE64_MAPPING : BASE64_MAPPING;

		var extra_Zero_Count = 0;
		for (var i = 0, len = binaryArray.length; i < len; i += 6) {
			var diff = (i + 6) - len;
			if (diff == 2) {
				extra_Zero_Count = 2;
			} else if (diff == 4) {
				extra_Zero_Count = 4;
			}
			var _tmpExtra_Zero_Count = extra_Zero_Count;
			while (--_tmpExtra_Zero_Count >= 0) {
				binaryArray.push(0);
			}
			base64_Index.push(_toDecimal(binaryArray.slice(i, i + 6)));
		}

		var base64 = '';
		for (var i = 0, len = base64_Index.length; i < len; ++i) {
			base64 += dictionary[base64_Index[i]];
		}

		for (var i = 0, len = extra_Zero_Count / 2; i < len; ++i) {
			base64 += '=';
		}
		return base64;
	};

	var _decode = function (_base64Str, url_safe) {
		var _len = _base64Str.length;
		var extra_Zero_Count = 0;
		var dictionary = url_safe ? URLSAFE_BASE64_MAPPING : BASE64_MAPPING;

		if (_base64Str.charAt(_len - 1) == '=') {
			if (_base64Str.charAt(_len - 2) == '=') {//两个等号说明补了4个0
				extra_Zero_Count = 4;
				_base64Str = _base64Str.substring(0, _len - 2);
			} else {//一个等号说明补了2个0
				extra_Zero_Count = 2;
				_base64Str = _base64Str.substring(0, _len - 1);
			}
		}

		var binaryArray = [];
		for (var i = 0, len = _base64Str.length; i < len; ++i) {
			var c = _base64Str.charAt(i);
			for (var j = 0, size = dictionary.length; j < size; ++j) {
				if (c == dictionary[j]) {
					var _tmp = _toBinary(j);
					/*不足6位的补0*/
					var _tmpLen = _tmp.length;
					if (6 - _tmpLen > 0) {
						for (var k = 6 - _tmpLen; k > 0; --k) {
							_tmp.unshift(0);
						}
					}
					binaryArray = binaryArray.concat(_tmp);
					break;
				}
			}
		}
		if (extra_Zero_Count > 0) {
			binaryArray = binaryArray.slice(0, binaryArray.length - extra_Zero_Count);
		}
		var str = _toUnicodeStr(binaryArray);
		return str;
	};

	var __BASE64 = {
		encode: function (str) {
			return _encode(str, false);
		},
		decode: function (base64Str) {
			return _decode(base64Str, false);
		},
		urlsafe_encode: function (str) {
			return _encode(str, true);
		},
		urlsafe_decode: function (base64Str) {
			return _decode(base64Str, true);
		}
	};

	return __BASE64;
}));
